The present invention relates to a probe and method for use in examining the electrical characteristics of a high-frequency semiconductor device, such as a monolithic microwave integrated circuit, which operates at a frequency of not lower than 800 MHz.
Conventionally, there has been known a probe for a high-frequency signal for use in examining the electric characteristics of a high-frequency semiconductor device, such as a monolithic microwave integrated circuit, which operates at a frequency of not lower than 800 MHz.
The characteristic impedance Zp of the probe is set equal to the characteristic impedance of the semiconductor device, or the circuit to be measured. For example, a high-frequency semiconductor device such as a monolithic microwave integrated circuit is designed so as to have a characteristic impedance of 50 xcexa9 in a state in which a semiconductor chip is mounted on a substrate. Then, the probe used for the semiconductor device is designed so as to have a characteristic impedance Zp of 50 xcexa9.
FIG. 20 is a diagram showing the construction of conventional high-frequency signal probes 150a and 150b (refer to Japanese Patent Laid-Open Publication No. HEI 6-244263). In the probe 150a, terminals 154a and 154c are ground terminals and connected to a measuring instrument 151 via grounding conductors 152a and 152b. The terminal 154b is a terminal for signal input and output use and connected to the measuring instrument 151 via a conductor 153 designed so that the impedance of the probe viewed from the circuit to be measured has a desired value Zp in order to match the impedance of the probe with the circuit to be measured.
With regard to the probe 150b, terminals 174a and 174c are ground terminals and connected to the measuring instrument 151 via grounding conductors 172a and 172b. The terminal 174b is a signal input terminal and connected to the measuring instrument 151 via a conductor 173 designed so that the characteristic impedance Z2 becomes Zp in order to match the impedance of the terminal with the circuit to be measured.
The electrical characteristics of the high-frequency semiconductor device that is the circuit to be measured are measured by first connecting terminals corresponding to the probes 150a and 150b to the ground electrode and the signal electrode of the semiconductor device and inputting or outputting a specified signal to or from the signal electrode via the probes 150a and 150b. 
In the aforementioned conventional probes 150a and 150b it has been hard to obtain the characteristic impedance Z2 equal to the designed impedance Zp due to an error caused by manufacturing inaccuracies and the influence of parasitic capacitance, parasitic inductance and so on included in the ground wiring and so on. From another point of view, it is required to produce a lot of prototypes whose parts are partially delicately changed from the designed values in order to obtain a probe having a correct characteristic impedance Zp of 50 xcexa9, and this has led to the problem that the manufacturing cost increases.
If a semiconductor chip is determined to be defective as the result of measurement of electric characteristics after being separated and assembled, then the whole board on which the semiconductor chip is mounted and specified wiring is provided is to be handled as a defective product, frequently resulting in waste.
The waste can be eliminated if the electrical characteristics of the semiconductor chip can be measured in the stage prior to the mounting on the board. However, in order to enable the aforementioned measurement, it is required to prepare a probe having the desired characteristic impedance Zp (not 50 xcexa9 but, for example, 6 xcexa9) determined inherently in each semiconductor chip.
As described above, the conventional technique requires the production of a lot of prototypes in order to obtain a probe having a characteristic impedance Zp of the specified characteristics. For this reason, it has been impractical in terms of manufacturing cost to prepare a probe having the characteristic impedance Zp corresponding to each semiconductor chip.
FIG. 21 is a diagram showing the construction of another probe 200 for measuring a high-frequency semiconductor device, different from the aforementioned conventional probes 150a and 150b (refer to Japanese Patent Laid-Open Publication No. HEI 3-283441). In this probe 200, terminals 206a and 206b are ground terminals. The terminal 207 is a signal input and output terminal that receives a signal from a circuit board to be tested and connected to a line 208 having three branch lines 208a, 208b and 208c. The branch lines 208a, 208b and 208c have their ends provided with capacitors 209a, 209b and 209c. In designing the probe 200, the adjustment of the impedance Zp of the probe 200 can be relatively simply performed by adjusting the values of the capacitors 209a, 209b and 209c. 
However, the values of the capacitors 209a, 209b and 209c can be changed discretely in steps of, for example, 1 pf. Furthermore, since the mounting positions of the capacitors are also fixed, it is difficult to accurately adjust the value of the impedance Zp to the desired value. Therefore, it is still required to produce a lot of prototypes whose parts have changed design values in order to obtain a probe of the desired impedance Zp, and therefore, the aforementioned various problems could not be effectively solved.
The object of the present invention is to provide a probe having a characteristic impedance Zp that can be accurately adjusted to a desired value with the production of a small number of prototypes. Another object of the present invention is to provide a method for using the probe in the examination of electrical characteristics of devices.
According to the first aspect of the present invention, there is provided a probe for a high-frequency signal used for an electric test in a high-frequency band of a circuit to be measured, the probe comprising: a signal terminal to be connected to a signal electrode of the circuit to be measured; a first line that has a specified impedance, one end connected to the signal terminal and at least one first region to which one end of a chip capacitor is connected; a second line that is connected to a terminal opposite to the end of the first line connected to the signal terminal and has a junction to be connected to a measuring instrument for executing the electric test at the remaining terminal and an impedance matched to the characteristic impedance of the measuring instrument; a ground terminal to be connected to the ground electrode of the circuit to be measured; and a ground conductor that is connected to the ground terminal and has at least one second region to which a remaining terminal of the chip capacitor is connected in one-to-one correspondence with the first region, wherein a chip capacitor of a specified capacitance value is mounted in specified positions within the first region and the second region so that an impedance of the probe viewed from the circuit to be measured has a desired value.
According to the probe for a high-frequency signal of the second aspect of the present invention, based on the probe of the first aspect, the ground conductor is formed on an insulating substrate having a back surface ground conductor and provided with a plurality of via holes connected to the back surface ground conductor, and an interval between each of the via holes and the signal terminal and an interval between via holes are each not greater than one fourth of a wavelength xcex of the high-frequency signal inputted to the signal terminal.
According to the probe for a high-frequency signal of the third aspect of the present invention, based on the probe of the first or second aspect, a specified chip inductor is inserted in the first line.
According to the probe for a high-frequency signal of the fourth aspect of the present invention, based on the probe of any one of the first through third aspects, a line that is branched from the ground conductor as the second region is provided, the chip capacitor is connected across the branched line and the first region, and an LC resonance circuit constructed of the branched line and the chip capacitor resonates with a higher harmonic at a multiple of the frequency of the signal inputted to the signal terminal.
According to the probe for a high-frequency signal of the fifth aspect of the present invention, based on the probe of any one of the first through fourth aspects, there is provided a high-impedance branch line that is branched from the vicinity of the signal terminal of the first line and has a terminal for detecting a potential of the signal terminal.
According to the probe for a high-frequency signal of the sixth aspect of the present invention, there is provided an isolator that has impedance characteristics corresponding to the frequency of the input signal between the first line and the second line, the impedance characteristics being identical to that of the isolator provided in the output section of the circuit to be measured.
According to the probe for a high-frequency signal of the seventh aspect of the present invention, based on the probe of any one of the first through sixth aspects, there is provided a conductor that is connected to the ground conductor and shields electromagnetic waves by covering the first line and the second line with interposition of a specified gap.
According to the present invention, there is provided a semiconductor device inspecting method using the probe of the first through seventh aspects of the present invention.